An apparatus is described in German Open Patent Application 24 17 527 in which gear wheels whose gear teeth spaces correspond in size to the thickness of the can covers and whose rotation is detected by an optical unit project into the motion path of the can covers in the stack. The can covers travelling past gaps provided in it are counted by an electronic counter and are assembled in a pile with a predetermined number of covers. An engaging piece on a sliding support or carriage is guided into the gap between the last cover of the pile and the following stack and is accelerated forwardly to separate the pile from the stack by the sliding support or carriage.
Another apparatus for separating piles of covers with equal numbers of covers from a longitudinally moving stack operates practically exclusively mechanically and uses no electronic control (German Open Patent Application 33 33 521).
The known apparatuses are comparatively expensive and operate with a comparatively low speed of up to approximately 500 workpieces and/or can covers per second. A satisfactory operation is only attainable when the workpieces to be counted and/or the can covers to be counted have very small tolerances in the vicinity of their edges which cooperate with the counter. In making can covers with edges rolled in and/or shaped for receiving sealing material, larger tolerances may not be avoidable because of differing working material properties and/or wear of tools. When the usability of the cover is not impaired in forming the edges with larger tolerances, it is desirable to form the covers with tolerances which are as large as possible during edge formation because of manufacturing engineering and economic considerations.